In the sphere of telecommunications there is, in many cases, a need for a very high transmission capacity. Very fast data transmission can be achieved by using optical transmission by way of modulated light signals.
In order to send a plurality of light signals over a common optical medium, wavelength division multiplexing (WDM) is used. The signals are sent by way of independent wavelength channels, which can exist simultaneously in one optical fibre.
The optical transmission can be achieved in optical bus networks which comprise a number of optically connected nodes adapted for reciprocal communication. In an optical bus network comprising N nodes connected in series to one another, communication between nodes can be achieved in both directions by using at least two fibres for this communication, at least one fibre of which is used for each signal distribution direction. Each node communicates with each other node by way of a unique wavelength channel. This means that at least N-1 wavelength channels will exist simultaneously on each optical fibre.
A network which facilitates continuous communication between all nodes even following a fibre fracture between two nodes is already known from U.S. Pat. No. 5,159,595. The network comprises a number of nodes which are connected to one another in an circular configuration. This configuration is suited, for example, to wavelength division multiplexing.
When interruption occurs between two nodes, the wavelength channels which are used for communication to or from the said two nodes must change direction. The number of channels on the signal path used after interruption must then be increased In the known network additional channel assignment is facilitated in that each node comprises one transmitter port and one receiver port respectively, by means of which arbitrary wavelength channels can be added to or removed from the bus network. This solution, however, is both technically and economically disadvantageous.